1. Field of the Invention
The present invention relates to a method for determining the position of a vehicle.
The invention is applicable where ever vehicles, preferably portal stacking trucks have to be moved into an exact position in relation to a container crane, so that no repositioning of the container crane is required.
2. The Prior Art
Container cranes are special portal container cranes for unloading ships, and also stacking cranes in a container depot. The transshipment of containers has been carried out until now with container cranes or portal stacking trucks only by manual operations. When the load is transferred to the container crane, the driver of the transport vehicle has to deposit the container approximately in the center below the container crane. For picking up the load with the container crane, the latter is repositioned, as a rule. Now, for fully automatic container cranes, the problem on hand is to always position the transport vehicle exactly in the center position below the container crane for transferring the load, so that no repositioning is required for picking up the load with the container crane. This requires that the transport vehicle is oriented in relation to the container crane with such precision that the container can be accurately set down.
A device for determining the position of a vehicle in relation to a container hoisting device is known from DE 36 06 363, in connection with which at least two sensors operating based on ultrasound assume with parallel axes an unchanged position in relation to a framework structure of the hoisting device; the transport vehicle is equipped with reflectors; evaluation devises are coupled to a detection device; and holding marks are required so that the positioning process can be carried out.
It is a drawback in connection with such a method, among other things, that means such a holding marks, reflectors and similar pieces of equipment have to be mounted in order to detect the position of the transport vehicle or of the container.
Therefore, an object of the invention is to develop a method by means of which a transport vehicle, preferably a portal vehicle orients itself vis-xc3xa1-vis a container crane without markings having to be attached to said crane, so that an automatic operation of the vehicle is assured in which the position of the vehicle in relation to the container crane is always exactly known.
This object is achieved according to the present invention.
The method as defined by the invention for the determination of the position of a vehicle in relation to a container crane is based on the fact that container cranes have a prominent contour up to a certain height. The vehicle, for example a portal stacking truck can orient itself on such a prominent contour. It is necessary for such orientation that, for example the portal stacking truck has a scanning device. Said scanner, for example a laser scanner, can be arranged on the top edge of the portal stacking truck in the driving direction. The laser scanner detects the posts of the portal crane as positioning aids. This can be accomplished in that the scanner detects the angle and the distance of the posts of the portal crane and transmits this information to an evaluating computer. The software of the evaluating computer contains data with respect to the contour of the posts of the container crane and in this way determines the exact position of the transport vehicle in relation to the posts of the container crane.
After the actual position of the portal stacking truck has been determined by means of the evaluating computer, a comparison is carried out with the nominal position into which a container has to be moved. By means of the drive and the drive control and continual comparison between the actual and the nominal data via a position controller, the vehicle with the container is maneuvered into the desired position until the data of the nominal and the actual positions correspond. An orientation takes place in this connection continually via the data of the posts of the container crane detected by the scanner.
It is advantageous for the method if a plurality of laser scanners is arranged on the vehicle. Such laser scanners may be arranged vertically or horizontally. Of decisive importance is that the positions of the laser scanners vis-à-vis the vehicle are balanced. However, it is advantageous if the laser scanner is mounted on the stacking truck horizontally at a level that permits clear orientation on the posts of the container crane.